Hand-harvest work in wine grape vineyards is physically demanding and exposes workers to a variety of ergonomics risk factors. Analysis of these exposures together with data on reported work-related injuries points to the risk of back injury as a prevention priority, in particular the lifting and carrying of tubs of cut grapes (weighing up to 80 pounds) during harvest. Our study evaluated the effectiveness of an intervention — the use of a smaller picking tub — on the incidence of musculoskeletal symptoms among workers during two harvest seasons. Reducing the weight of the picking tub by 19% (to below 50 pounds) resulted in a five-fold reduction in workers’ post-season musculoskeletal symptom scores, without significant reductions in productivity.